Can I hurt myself with a vibrator?

Short Answer:
Vibrators are as safe as any other small electrical device as long as
they're used according the instructions and with common sense.

Long Answer: With
battery-powered vibrators there is a minimal risk of electrical shock,
and with plug-in vibrators there is the same risk of electrocution as
with any appliance, but in general vibrators pose no more of a risk than
a flashlight or toaster. Use common sense and keep them away from water
unless they are designed to be waterproof. Make sure that all external
wires are secure and not frayed. Don't use your vibrator so much that
the motor overheats; it could cause a minor burn or start a fire.

As far as other injuries,
common sense should also keep you out of trouble. Don't ever force
insertion of a vibrator into the vagina or anus, and don't insert a
vibrator completely into either. You may have difficulty getting it out.

Of course, if you do
anything too much, too often, you may hurt yourself, so try not to
overdo it with your vibrator. The skin of the genitals is sensitive, and
persistent or prolonged friction or stimulation can cause irritation.
Some people find that using a vibrator frequently can make their
genitals feel less sensitive. If that's the case, lay off the vibrator
for a while and go back to manual stimulation.

Some vibrators may be
awkward to hold or use, so if you have carpal tunnel syndrome or
tendonitis in your hands or wrists, using a vibrator may aggravate it.
Shop around for a more ergonomic model; vibrators with longer handles,
like the Hitachi Magic Wand or the Flex-O-Pleaser, are easier for some
people to use.